This works because gravity holds you firmly on the ground, and your feet stay put because of friction with the floor.

CNN: Kepler or not, we'll find life in space

But while this works in Latvia, a relatively marketised economy, in Greece there is a lot of friction - and not just because of organised labour resistance.

BBC: Greece: How do you save an economy from going bust?

But if one person's mind was changed because of her actions, Foster said it was worth the nerves and friction.

CNN: No one should be fired for being gay

For every company that fails for business reasons, ten more fail because like so many rock bands, they are overwhelmed by the friction of conflicting agendas, personal animosities, and pervasive mistrust.

FORBES: Leadership Lessons from an Unsung Hero

Some friction with post-communist Russia was inevitable, if only because of Russian resentment of America's new geopolitical pre-eminence.

ECONOMIST: Russia��s self-isolation

My wife, who was born in Guadalajara and came to the United States legally as a child, reminds me that there is friction between Mexicans and Mexican-Americans because Mexicans have a firmer grasp of who they are and Mexican-Americans resent that.

CNN: My Mexican-American identity crisis

This friction has emboldened those Russians who would prefer to stay out, either because they dislike the idea of Russia joining anything, or because they fear for vulnerable sectors, such as agriculture: Russian produce will struggle to compete with subsidised European fare.

ECONOMIST: Russia and the WTO

From its perspective, the policies may even be regarded as a success because the migration of Han Chinese into the sparsely populated regions enhances government control over the longer term, regardless of the friction it may create.

WSJ: The Urumqi Effect